This invention relates to a circular comb comprising an essentially cylindrical support member being rotatable around its cylinder axis, and a comb member extending around a part of the peripheral surface of the support member and being rotatable therewith, wherein a channel and/or groove, extending essentially in a circumferential direction of the support member is arranged beneath the tines of the comb member in the support member and/or the comb member and/or between the support member and the comb member said channel and/or groove having a first orifice facing in a rotational direction of the support member and a second orifice facing in a direction opposite to the rotational direction of the support member.
Circular combs of the above general type are applied when working textile fibers in combing machines for removing short fibers and neps from the raw stock material having been previously subjected to a carding process. By this working process, the staple, i.e. the length of the fibers of the raw stock material is unified. For this purpose, the combing machine is generally positioned between the carding machine and the drafting frame in a fiber processing plant.
In the combing machine, a fiber tuft consisting of already carded fibers is held by nipper jaws and the tines of the circular comb pass through the likewise held fiber tuft. Thereafter, the fiber tuft is connected to an already combed fiber band. However, it is also possible to comb the fiber tuft after having it connected to the fiber band. The overall processing comprising engaging of the tines of the comb member into the fiber tuft, combing and connecting until the beginning of the engagement of the circular comb into a fiber tuft successively fed to the nipper jaws is hereinafter referred to as one "nip of the comb".
In ordinary circular combs, the support member is formed essentially cylindrical and the comb member extends around a part of the peripheral surface of the support member. During operation, the circular comb is rotated around its cylinder axis and with respect to the nipper jaws, it is positioned in such a manner that whereas the tines of the comb member may pass through the fiber tuft held by the nipper jaws, the support member does not represent a hinderance for connecting the combed fiber tuft with the fiber band when further rotating the circular comb. For this purpose, the circular comb is constructed so as to comprise a comb member attached to the cylindrical support member and expanding the support member in a radial direction, wherein a said comb member is provided with tines extending essentially radially outwardly. At the beginning of the development of circular combs, the tines were formed by round needles. By employing like circular combs a processing speed of 100 to 110 nips of the comb per minute could be achieved while simultaneously maintaining a satisfying combing effect. By the replacement of the round needles by saw-toothed wires, the processing speed could be raised up to 350 nips of the comb per minute without negatively effecting the combing effect. However, it has been shown that a further increase of the processing speed could not be achieved even when applying circular combs being provided with saw-toothed wires without effecting an insufficient combing effect.
A circular comb showing the features of the precharacterizing portion of claim 1 is known from CH-673 290 A5. In the circular comb disclosed in this document, an air conduit is disposed between the inner surface of the combing segment being provided with an airfoil profile and the outer surface of a cylindrical support member. By combining the air conduit with the airfoil type combing segment, in this known circular comb, a suction is generated in a region above the combing segment and a fiber tuft to be combed is fed to the tines of the comb. For this purpose, the air conduit is provided with a cross section increasing in a direction opposite to the rotational direction of the comb. For avoiding the formation of turbulences above the combing segment, generally effected by the above arrangement a comparatively thick projection is provided at the end of the combing segment facing in the rotational direction of the comb. For the purpose of ensuring that the teeth or needles of the combing segment engage into the fiber tuft as early as possible inspire of the dynamic pressure generated in front of the projection in the circular comb proposed in this document, .the teeth or needles are arranged in a position shifted backwardly with respect to the projection. Thus, a combing segment of a like circular comb has an overall length extending over that of the section provided with needles or teeth. Consequently, when using a like circular comb at a given processing speed, i.e. at a given number of nips of the comb per minute, the period of time in which the connection of the combed fiber tuft with the previously combed fiber band is reduced as compared to that available when employing an ordinary circular comb to thereby limit the processing speed achievable by the employment of circular combs disclosed in CH 673 290 A5.